Disc drives are data storage devices that store digital data in magnetic form on a rotating storage medium, such as a disc. Read/write transducers or “heads” are used to transfer data between the discs and an external environment. Typically, a voice coil motor or other type of actuator is used to position the heads with respect to the disc surfaces. The actuator body pivots about a bearing assembly mounted on a base plate of the disc drive at a position closely adjacent to the outer extreme of the discs. The heads read data and transfer it along an actuator arm to a preamplifier which amplifies the signals coming from the heads.
A flex circuit provides an electrical pathway between the preamplifier of the actuator arm and a disc drive circuit board mounted on an exterior side of the base plate opposite the actuator and discs. The flex circuit also sends drive signals to the voice coil motor causing the actuator arm to pivot about the bearing assembly thereby changing the position of the head relative to the disc. The flex circuit typically terminates at a pass-through connector mounted to a flex circuit bracket, where the connector extends through an opening in the base plate of the disc drive and contacts the circuit board fixed to the exterior side of the base plate. A gasket or other type of seal typically prevents air from entering the disc drive through the opening in the base plate below the flex circuit bracket.
In addition to the sealed opening below the flex circuit bracket, other openings in the disc drive base plate and top cover are typically sealed to prevent contaminants from entering the sterile disc drive environment. This is particularly important due to the fact that the read/write heads actually “fly” a very small distance above the spinning discs. Thus, even a microscopically small particle on the surface of the disc could cause a head “crash.” Recirculation filters are typically placed within the disc drive interior to help eliminate any particles that might be sealed within the drive during the manufacturing process. These recirculation filters take advantage of the air currents generated within the drive interior to capture rogue particles.
In addition to the threat of dust or other particulates, a further cause of “head crashes” within a disc drive relates to changes in temperature and pressure within the drive during operation of the drive. The interior temperature of a disc drive can vary greatly due to the operation of the different motors within the drive and the rapidly spinning discs, as well as the fact that the disc drive is typically contained within a closed computer case that also experiences a rise in temperature during operation of the computer. To prevent changing temperatures from altering the air pressure (and thus the fly height of the heads) within the disc drive, a small breather port is typically formed in the disc drive case to equalize the air pressure in the drive with the ambient pressure outside of the drive. To prevent particulates and caustic chemicals contained in the ambient air from contaminating the interior of the drive, a breather filter is typically attached to the breather port within the drive. The breather filter can also include a desiccant or other material to absorb water vapor.
Prior art breather filters have suffered from a number of drawbacks relating mainly to longevity and ease of installation. With regard to longevity, the cramped conditions within present disc drive cases necessitate a small filter size that typically cannot hold a sufficient amount of chemical adsorbent (such as activated charcoal) to last over the rated lifetime of the drive. With regard to installation, breather ports are typically formed in the top cover of a disc drive while the breather filters are adhered to an inner surface of the top cover by a double-sided tape or a pressure sensitive adhesive. However, the use of such adhesives may cause undesirable outgassing within the interior of the drive, while simultaneously creating problems on the assembly line should it be necessary to remove the filter from the cover during a rework of the drive. Furthermore, current manufacturing trends favor a “top-down” assembly system where it is desirable to attach as many components as possible to the base plate of the drive while avoiding adhering components to the inner surface of the top cover.
It is thus desirable to provide a breather filter for a disc drive that maximizes the life expectancy of the filter material while avoiding the installation problems commonly found with prior art breather filters.